Red Faction guerilla. The previous two games weren't amazing, but they were fun, and destroying scenery was an awesome idea. Guerilla took things up a notch, using an engine that looked amazing, and used really good physics. Unfortunately, it was made about the same time that all developers seemed to be hot for sandbox games, totally eliminating any decent plot, and making missions seem boring and repetetive - go rescue x hostage, destroy y building, come back when you have z money etc.
If the game had less missions, and they made them more interesting (quality over quantity), i'd have been much happier. That said, i only played the game for 2 hours before i got sick of it, so maybe i'm not the best person to comment..